1. Field of the Invention
The present invention relates to a device for transporting materials over fragile structures and more particularly to such a device which can be used individually or in multiples to transport such materials as sheet metal over the sloped roofs of buildings during construction without damaging the roofs; which serves as a supply and support station during construction; and which minimizes the risk that workers or the device itself could fall from the roof.
2. Description of the Prior Art
The Bertelsen U.S. Pat. No. 3,047,499 relates to a self-propelled vehicle track having an air pressure system for urging the load of the power mechanisms out of physical contact with the ground engaging portion of the track.
The Hendricks U.S. Pat. No. 3,398,806 discloses a self-propelled crawler-type mobile platform utilizing two matching individually powered crawler-type dollies ridigly tied together in spaced relation by a spanner member having a load carrying deck and operated from a position remote from the dollies for use on a sub-roof of a building.
The Cummins U.S. Pat. No. 3,761,040 is directed to a remote control helicopter transport device having tracks and method.
The Wood U.S. Pat. No. 3,950,038 discloses a fluid bearing track device having a pair of rollers about which is extended a ribbed belt.
There are a great many problems in large construction operations incident to the use of lightweight materials. This is particularly true in the installation of exterior weather barrier roofs such as are used on large steel buildings. Characteristically such roofs are formed by sections of lightweight, corrugated sheet metal mounted on beams, or purlins, running longitudinally of the roof. Depending upon the area of the country involved, such roofs are normally inclined to a peak in a ratio of height to span of one to twelve or four to twelve. Conventional practice calls for the sections to be lifted to the roof and stacked. The workers then carry the sections or sheets along the purlins from the stack for individual positioning and installation. Due to the size of such roofs, a great deal of time is expended in carrying each section from the stack to the position in which it is to be installed. Since, even where the worker is moving along a portion of the roof on which the sheet metal has been installed, it is necessary to move only along the purlins to avoid damaging the lightweight sheet metal, the difficulty, expenditure of time and danger involved in installing the sections of sheet metal in this conventional fashion are considerable. Furthermore, the workers are confronted with such other difficulties as the lack of a convenient power source for their powered tools and the lack of a convenient means for securing themselves to the roof to avoid being injured by a fall.
While it is known to use remote controlled vehicles of a variety of types for transporting materials, there has heretofore been no such vehicle which could assist in the installation of sheet material to form exterior weather barrier roofs and the like because of the very fragile nature of such roof construction and because of the slope of such roofs. These difficulties are far more severe than those encountered in the construction of sub-roofs where heavier gauge metal and more plentiful supporting beams must be employed to support the weight of concrete which is subsequently poured over the sheet metal to complete the sub-roof. Furthermore, such sub-roofs are not inclined as in the case of exterior roofs.
Therefore, it has long been known that it would be desirable to have a device for transporting materials across fragile structures which possesses the capability for operation on a sloped, lightweight roof or similar structure to allow the transport of sheet materials thereacross during construction while minimizing the risk of damage to the structure so formed and which serves as a supply and support vehicle for workers during such construction.